问题描述

Java语言程序设计第4章编程练习题1求问

import java.util.Scanner;

public class Practice {
    public static void main(String[] args) {
        Scanner input = new Scanner(System.in);
        int data = 0;
        int positive = 0;
        int negative = 0;
        int sum = 0;
        int count = 0;
        System.out.print("Enter int value (0 for exit):");

        do {
            data = input.nextInt();
            if (data > 0)
                positive += 1;
            else
                negative += 1;
            sum += data;
            count += 1;
        }while (input.hasNextInt() && data != 0);

        double average = sum / count;
        System.out.println("The totla is " + sum);
        System.out.println("The average is " + average);
    }
}

执行的时候不显示结果，0退出不了。怎样能够达到输出这样的结果啊？

• Enter int value(0 for exit):
• 1 2 -1 3 0 (enter)
• The number of positives is 3
• The number of positives is 1
• The number of positives is 1The total is 5
• The average is 1.25

解决方案

将while循环里面的条件交换一下位置就行了
while(data!=0 && input.hasNextInt())

解决方案二：

原因是input.hasNextInt()放在前面的话，当最后一个int值处理之后会等待输入，所以不会执行后面的输出部分的代码
另外最后记得加上input.close();养成好的习惯

解决方案三：

把Scanner input = new Scanner(System.in);放在do循环里

解决方案四：

     Scanner input = new Scanner(System.in);
        int data = 0;
        int positive = 0;
        int negative = 0;
        int sum = 0;
        int count = 0;
        System.out.print("Enter int value (0 for exit):");

        do {
            data = input.nextInt();
            if (data > 0)
                positive += 1;
            else
                negative += 1;
            sum += data;
            count += 1;
        }while (data != 0);
        double average = sum / count;
        System.out.println("The positive is " + positive);
        System.out.println("The negative is " + negative);
        System.out.println("The totla is " + sum);
        System.out.println("The average is " + average);
    }

解决方案五：

加个标记public static void main(String[] args) {
Scanner sc = new Scanner(System.in);
int data = 0;
int positive = 0;
int negative = 0;
int sum = 0;
int count = 0;
boolean flag = true;
do {
System.out.println("Enter int value (0 for exit):");
data = sc.nextInt();
if (data > 0)
positive += 1;
else
negative += 1;
sum += data;
count += 1;
System.out.println("是否需要再次输入 Y/N");
if ("N".equals(sc.next())) {
flag = false;
}
} while (flag && data != 0);

    double average = sum / count;
    System.out.println("The totla is " + sum);
    System.out.println("The average is " + average);
}你的hasNextInt方法只是加一个扫描器，不太好判断，还是直接加个标记好一些。